6 files changed, 63 insertions, 8 deletions
diff --git a/include/mbgl/storage/resource.hpp b/include/mbgl/storage/resource.hpp
index 318fa389f4..d9da494e4d 100644
--- a/include/mbgl/storage/resource.hpp
+++ b/include/mbgl/storage/resource.hpp
@@ -42,12 +42,23 @@ public:
         All         = Cache | Network,
     };
 
+    enum class Compression : bool {
+        // The data will be an uncompressed blob, even if it was obtained in compressed form.
+        Uncompressed = false,
+
+        // The data will be returned compressed if it was already obtained in compressed form,
+        // and uncompressed otherwise.
+        PreferCompressed = true,
+    };
+
     Resource(Kind kind_,
              std::string url_,
              optional<TileData> tileData_ = {},
-             LoadingMethod loadingMethod_ = LoadingMethod::All)
+             LoadingMethod loadingMethod_ = LoadingMethod::All,
+             Compression compression_ = Compression::PreferCompressed)
         : kind(kind_),
           loadingMethod(loadingMethod_),
+          compression(compression_),
           url(std::move(url_)),
           tileData(std::move(tileData_)) {
     }
@@ -72,6 +83,7 @@ public:
     
     Kind kind;
     LoadingMethod loadingMethod;
+    Compression compression;
     std::string url;
 
     // Includes auxiliary data if this is a tile request.
@@ -80,7 +92,7 @@ public:
     optional<Timestamp> priorModified = {};
     optional<Timestamp> priorExpires = {};
     optional<std::string> priorEtag = {};
-    std::shared_ptr<const std::string> priorData;
+    Blob priorData;
 };
 
 
diff --git a/include/mbgl/storage/response.hpp b/include/mbgl/storage/response.hpp
index 508400141b..81a84effb7 100644
--- a/include/mbgl/storage/response.hpp
+++ b/include/mbgl/storage/response.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/util/chrono.hpp>
 #include <mbgl/util/optional.hpp>
+#include <mbgl/util/blob.hpp>
 
 #include <string>
 #include <memory>
@@ -31,7 +32,7 @@ public:
     bool mustRevalidate = false;
 
     // The actual data of the response. Present only for non-error, non-notModified responses.
-    std::shared_ptr<const std::string> data;
+    Blob data;
 
     optional<Timestamp> modified;
     optional<Timestamp> expires;
diff --git a/include/mbgl/style/style.hpp b/include/mbgl/style/style.hpp
index d6fdbd8f2c..dffdbf99ec 100644
--- a/include/mbgl/style/style.hpp
+++ b/include/mbgl/style/style.hpp
@@ -3,6 +3,7 @@
 #include <mbgl/style/transition_options.hpp>
 #include <mbgl/map/camera.hpp>
 #include <mbgl/util/geo.hpp>
+#include <mbgl/util/blob.hpp>
 
 #include <string>
 #include <vector>
@@ -25,10 +26,10 @@ public:
     Style(Scheduler&, FileSource&, float pixelRatio);
     ~Style();
 
-    void loadJSON(const std::string&);
+    void loadJSON(Blob);
     void loadURL(const std::string&);
 
-    std::string getJSON() const;
+    Blob getJSON() const;
     std::string getURL() const;
 
     // Defaults
diff --git a/include/mbgl/util/blob.hpp b/include/mbgl/util/blob.hpp
new file mode 100644
index 0000000000..df8fddc773
--- /dev/null
+++ b/include/mbgl/util/blob.hpp
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <memory>
+#include <string>
+
+namespace mbgl {
+
+class Blob {
+public:
+    Blob();
+    Blob(std::shared_ptr<const std::string> bytes, bool gzip);
+    Blob(std::string&& bytes, bool compressed);
+
+    // Return uncompressed/compressed data.
+    std::shared_ptr<const std::string> uncompressedData() const;
+    std::shared_ptr<const std::string> compressedData() const;
+
+    // Transform the blob to being uncompressed.
+    void uncompress();
+
+    bool isCompressed() const {
+        return compressed;
+    }
+
+    explicit operator bool() const {
+        return (bool)bytes;
+    }
+
+private:
+    std::shared_ptr<const std::string> bytes;
+    bool compressed;
+};
+
+} // namespace mbgl
diff --git a/include/mbgl/util/compression.hpp b/include/mbgl/util/compression.hpp
index 93a3ddb8bc..cbce764683 100644
--- a/include/mbgl/util/compression.hpp
+++ b/include/mbgl/util/compression.hpp
@@ -5,8 +5,15 @@
 namespace mbgl {
 namespace util {
 
+// Compresses data with the deflate algorithm.
 std::string compress(const std::string& raw);
+
+// Decompresses data that is in deflate format, optionally wrapped in a gzip container.
 std::string decompress(const std::string& raw);
 
+// Returns true when there's a good chance that the string can be compressed.
+// In particular, it returns false when the data is an already compressed image format.
+bool isCompressible(const std::string& raw);
+
 } // namespace util
 } // namespace mbgl
diff --git a/include/mbgl/util/image.hpp b/include/mbgl/util/image.hpp
index 4887058f79..1cb3cca8c9 100644
--- a/include/mbgl/util/image.hpp
+++ b/include/mbgl/util/image.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/geometry.hpp>
+#include <mbgl/util/blob.hpp>
 #include <mbgl/util/size.hpp>
 
 #include <string>
@@ -170,8 +171,7 @@ using UnassociatedImage = Image<ImageAlphaMode::Unassociated>;
 using PremultipliedImage = Image<ImageAlphaMode::Premultiplied>;
 using AlphaImage = Image<ImageAlphaMode::Exclusive>;
 
-// TODO: don't use std::string for binary data.
-PremultipliedImage decodeImage(const std::string&);
-std::string encodePNG(const PremultipliedImage&);
+PremultipliedImage decodeImage(Blob);
+Blob encodePNG(const PremultipliedImage&);
 
 } // namespace mbgl